给JDBC换个装——连接解耦

package jdbc;

        import org.junit.jupiter.api.Test;

        import java.sql.Connection;
        import java.sql.DriverManager;
        import java.sql.SQLException;

public class JDBCUtils {
    public static Connection connection;
    private static String url="jdbc:mysql://localhost:3306/aaa?useUnicode=true&characterEncoding=utf-8";
    private static String username="root";
    private static String password="root";

    static{
        try {
            Class.forName("com.mysql.jdbc.Driver");
            connection = DriverManager.getConnection(url,username,password);

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection(){
        return connection;
    }

    @Test
    public void test(){
        Connection connection = JDBCUtils.getConnection();
        System.out.println(connection);
    }
}

package jdbc;

import org.junit.jupiter.api.Test;

import java.io

FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

public class JDBCUtils2 {
    private static Connection connection;
    private static String url;
    private static String username;
    private static String password;

    static {
        try {
            //动态加载驱动
            Class.forName("com.mysql.jdbc.Driver");
            //加载配置文件
            Properties properties = new Properties();
            properties.load(new FileInputStream("src/main/java/db.properties"));
            url = properties.getProperty("url");
            username = properties.getProperty("username");
            password = properties.getProperty("password");

            connection = DriverManager.getConnection(url,username,password);


        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection(){
        return connection;
    }

    @Test
    public void test(){
        Connection connection = JDBCUtils2.getConnection();
        System.out.println(connection);
    }
}